Biblical-scale task tackled by elite window cleaners
A PROJECT in Wells which cost half a million pounds and took almost four years is nearing its final stages. And it will be more than worth the effort, as reporter Jack Clare learns from those behind the cathedral's Jesse Window conservation.
THE painstaking £500,000 conservation of Wells Cathedral's great Jesse tree window has been in progress since October 2010.
The conservation work is being carried out by a local workforce of eight experts from highly specialised stained glass company Holy Well Glass. Around three-quarters of the work has now reached completion.
This project, however, is very different from other large-scale preservation strategies undertaken on major cathedrals.
Holy Well Glass director Dan Humphries: "Unusually, there is next to no restoration to the original windows, only conservation methods to preserve what is already there."
These processes include removing each metre square panel to a workshop environment, before taking detailed rubbings for reassembly purposes. Any excess glass cement can then be removed, and the perimeter leads taken off.
This allows the panel to relax and lie flat, correcting any bowing which has taken place while the glass has been vertical for hundreds of years. Following this, the panel is partially dismantled and each individual piece of glass is meticulously cleaned with a 50:50 solution of acetone and deionised water.
Any broken pieces are edge-bonded with resin, and 1mm thick float glass is used as a backplate to restore painted areas that have faded over time to their former glory.
Finally the panels can be pieced back together ready for reinstallation. The entire window measures around nine metres high and seven metres wide.
Modern technology has also played a major role in the project in the form of isothermal glazing. This involves the installation of a secondary layer of protective glazing around four inches outside the ancient window, in the least obtrusive manner possible.
The medieval glass is then ventilated at the top and bottom, allowing the warmer internal air to circulate between the two surfaces of glass.
This protects the medieval window from the highly damaging long-term effects of condensation cycles, and simultaneously shields it from the ravages of the weather.
Mr Humphries believes this large-scale work is a great opportunity to celebrate the window: "It's massively under-publicised compared with the historically important glass of other cathedrals.
"There's really nothing else like the Jesse Window in Europe. The scale of the window and the level of original glass is pretty much unheard of."
The window depicts the ancestry of Christ, from the recumbent Jesse at the base, through to the crucifixion at the top, all in the form of a giant genealogical tree.
Fellow company director Steve Clare said: "The window has an incredible history of survival, remaining untouched through the iconoclasm of generations."
Much of the medieval glass in the cathedral, including that of the Lady Chapel, only survives in a fragmented state. The Jesse Window is the exception, having survived the reformation and English civil war largely unscathed.
The safety of the window has been ensured over generations by its height and inaccessibility. During the civil war, the first soldier who tried to climb up to destroy the window anecdotally fell to his death, putting off any further attempts.
Reiterating the importance of recognising the window as a major work of art, Mr Humphries added: "It would be a shame for local residents to have such a treasure on their doorstep and not be made aware of its significance."
Work on the Jesse window is currently on schedule and due to finish in July.